1. Field of the Invention
The invention relates to a control apparatus for a vehicle transmission including a continuously variable transmission mechanism and a gear mechanism that are provided in parallel with each other between a driving force source and a drive wheel.
2. Description of Related Art
There is well known a vehicle transmission including a belt-type continuously variable transmission mechanism and a gear mechanism that are provided in parallel with each other between an input rotating member and an output rotating member. The gear mechanism has a predetermined gear stage. The power of a driving force source is transmitted to the input rotating member. The output rotating member outputs the power to a drive wheel. This is, for example, a vehicle transmission described in Japanese Patent Application Publication No. 63-28740 (JP 63-28740 A). JP 63-28740 A describes a vehicle including a continuously variable transmission path and a direct drive path provided in parallel with each other between an input rotating member and an output rotating member. A continuously variable transmission is interposed in the continuously variable transmission path. The direct drive path has a fixed speed gear ratio close to the highest vehicle speed-side (highest-side) speed gear ratio (highest speed gear ratio) in the continuously variable transmission path. For example, the highest vehicle speed-side (highest-side) speed gear ratio (highest speed gear ratio) is a maximum gear ratio. In addition, JP 63-28740 A describes that, while the vehicle is traveling by using the direct drive path, a loss torque in the idling continuously variable transmission is reduced by controlling the speed gear ratio of the continuously variable transmission, which continues idling in a no-load state, to a low vehicle speed-side (low-side) optimal speed gear ratio with respect to the highest speed gear ratio. The low vehicle speed-side optimal speed gear ratio is, for example, an intermediate speed gear ratio that is the speed gear ratio “1”.